1. Field of the Invention
The present invention relates to an engine cover for protecting a surface of an engine.
2. Description of the Related Art
An engine cover is arranged on, for example, an upper surface of a cylinder head of an engine. For maintenance of the engine, the engine cover needs to be detachably mounted to the engine. Therefore, a mounting structure including a protruded member and a recessed member, as described in U.S. Pat. No. 6,206,604 for example, is often used.
FIG. 14 shows a sectional view of a mounting structure for an engine cover including a protruded member and a recessed member (hereinafter abbreviated as “mounting structure” according to circumstances). A protruded member 101 of a mounting structure 100 is made of metal and presents a bolt shape. The protruded member 101 includes a screw section 103, a neck 104, and a head 105. The screw section 103 is screwed into an upper surface of a cylinder head 102. The neck 104 is arranged above the screw section 103. The head 105 is arranged above the neck 104. The head 105 presents a spherical shape. The head 105 has a larger diameter than the neck 104.
The recessed member 106 is made of rubber and presents a thin cup shape opening downward. The recessed member 106 is locked to a tip of a mounting seat 109 which is vertically provided from a lower surface of an engine cover 108. A concave 107 of a spherical shape in its back is arranged substantially in a center in a radial direction of the recessed member 106. The head 105 is press-fitted in the concave 107.
According to the mounting structure 100, the engine cover 108 can be mounted to the cylinder head 102 by press-fitting the head 105 into the concave 107. In addition, the engine cover 108 can be detached from the cylinder head 102 by pulling the head 105 out of the concave 107.
Incidentally, a clearance 110 is provided between the concave 107 of the recessed member 106. and an external surface 111. If the clearance 110 is provided, the concave 107 easily expands when the protruded member 101 is press-fitted into the recessed member 106. Therefore, a press-fit resistance is reduced. However, if the clearance 110 is provided, a thickness of a portion surrounding the concave 107 of the recessed member 106 is reduced. Consequently, it is likely that the head 105 breaks through the portion surrounding the concave 107 of the recessed member 106 at the time of mounting work of the engine cover 108.
In addition, since the press-fit resistance is low, the head 105 easily slips out of the concave 107 due to engine drive vibration or the like after the engine cover 108 is mounted. In other words, the protruded member 101 easily slips out of the recessed member 106. That is, the engine cover 108 drops off easily.
Further, the clearance 110 acts as a swing allowance of the head 105 after the engine cover 108 is mounted. In other words, the head can relatively swing by the clearance 110. Consequently, it is likely that the engine cover 108 becomes unsteady with respect to the cylinder head 102 due to engine drive vibration or the like.
Therefore, JP-UM-A-55-67329 introduces a mounting structure in which an engine cover is mounted to a cylinder block in a state in which a head of a protruded member projects to a side of a front surface of the engine cover. FIG. 15 shows a sectional view of another mounting structure described in the reference. Note that portions corresponding to those in FIG. 14 are denoted by the same reference numerals. Amounting hole 112 is opened in the engine cover 108. A rubber ring 113 is fit into an internal circumference side of the mounting hole 112. The protruded member 101 is vertically provided on the surface of the cylinder block 114. The protruded member 101 is press-fitted on an internal circumference side of the rubber ring 113. The head 105 projects to the side of the front surface of the engine cover 108. An internal circumferential surface of the rubber ring 113 is in pressed contact with the neck 104.
According to the mounting structure 100 described in JP-UM-A-55-67329, the neck 104 is tightened by the rubber ring 113 which is compressed between the neck 104 and the mounting hole 112. Thus, the neck 104, that is, the protruded member 101 does not easily slip out of the rubber ring 113. In other words, the engine cover 108 does not drop off easily. In addition, the unsteadiness of the engine cover 108 due to the engine drive vibration is also small. In other words, the mounting structure has high vibration damping properties.
However, according to the mounting structure 100 described in JP-UM-A-55-67329, the head 105 projects to the side of the front surface of the engine cover 108. Thus, its appearance is degraded. In addition, the uneasiness of the protruded member 101 to slip out of the rubber ring 113 and the high vibration damping properties depend upon the thickness of the rubber ring 113. In other words, in the case in which the rubber ring 113 is thin, the rubber ring 113 curves excessively between the internal circumferential surface of the mounting hole 112 and the external circumferential surface of the neck 104. Thus, a press-contacting force applied to the neck 104 from the rubber ring 113 is reduced.
Incidentally, in recent years, from the need to protect pedestrians, a shock absorbing space is often secured between a hood panel and an engine side member in an engine room. For example, in the case in which an object of collision such as a pedestrian is hit to fall on the hood panel, the hood panel sinks by the shock absorbing space. Collision energy of the object of collision is absorbed by this sinking of the hood panel. A width of the shock absorbing space and an amount of collision energy absorption are proportional to each other. Therefore, it is desirable that the shock absorbing space is as large as possible.
However, an engine cover is disposed above the engine side member as described above. In other words, the engine cover occupies a part of the shock absorbing space. Therefore, the amount of collision energy absorption decreases by the space occupied by the engine cover.
Thus, JP-A-2000-203378 introduces an engine cover in which shock absorbing means is integrally formed. The shock absorbing means is arranged between a front surface of the engine cover and a rear surface of a hood panel. In other words, the shock absorbing means occupies a part of a shock absorbing space. As described above, in the case in which an object of collision is hit to fall on the hood panel, the hood panel sinks. At this point, the shock absorbing means is destroyed by collision energy. In other words, the collision energy is converted into destruction energy. The collision energy of the object of collision is absorbed by this energy conversion.
Incidentally, the engine cover is a member projecting largely in the engine room. Thus, impression of the entire engine room changes significantly depending upon a degree of a design characteristic of the engine cover. Therefore, the engine cover described in the reference has a degraded appearance.
In addition, ports such as an engine oil inlet are often opened in the engine cover. These ports are required to be opened in portions corresponding to ports on the engine side on a rear side of the engine cover, respectively. Consequently, if the shock absorbing means is arranged on the front surface of the engine cover, it becomes difficult to open the ports in the predetermined portions. Thus, it is difficult to open the ports in the engine cover described in JP-A-2000-203378.